Acquisition of channel state information

ABSTRACT

In an aspect of the disclosure, a method, a computer-readable medium, and an apparatus are provided. The apparatus may be a UE. The UE measures, at a first time point, a first set of reference signals to determine a first set of values corresponding to a set of CSI parameters. The UE determines value differences between the first set of values and a set of reference values corresponding to the set of CSI parameters. The UE sends a first CSI report including variation indicators indicating the value differences.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims the benefits of U.S. Provisional ApplicationSer. No. 63/184,821, entitled “ACQUISITION FOR CHANNEL STATEINFORMATION” and filed on May 6, 2021, which is expressly incorporatedby reference herein in its entirety.

BACKGROUND Field

The present disclosure relates generally to communication systems, andmore particularly, to techniques of reporting channel state information(CSI) at a user equipment.

Background

The statements in this section merely provide background informationrelated to the present disclosure and may not constitute prior art.

Wireless communication systems are widely deployed to provide varioustelecommunication services such as telephony, video, data, messaging,and broadcasts. Typical wireless communication systems may employmultiple-access technologies capable of supporting communication withmultiple users by sharing available system resources. Examples of suchmultiple-access technologies include code division multiple access(CDMA) systems, time division multiple access (TDMA) systems, frequencydivision multiple access (FDMA) systems, orthogonal frequency divisionmultiple access (OFDMA) systems, single-carrier frequency divisionmultiple access (SC-FDMA) systems, and time division synchronous codedivision multiple access (TD-SCDMA) systems.

These multiple access technologies have been adopted in varioustelecommunication standards to provide a common protocol that enablesdifferent wireless devices to communicate on a municipal, national,regional, and even global level. An example telecommunication standardis 5G New Radio (NR). 5G NR is part of a continuous mobile broadbandevolution promulgated by Third Generation Partnership Project (3GPP) tomeet new requirements associated with latency, reliability, security,scalability (e.g., with Internet of Things (IoT)), and otherrequirements. Some aspects of 5G NR may be based on the 4G Long TermEvolution (LTE) standard. There exists a need for further improvementsin 5G NR technology. These improvements may also be applicable to othermulti-access technologies and the telecommunication standards thatemploy these technologies.

SUMMARY

The following presents a simplified summary of one or more aspects inorder to provide a basic understanding of such aspects. This summary isnot an extensive overview of all contemplated aspects, and is intendedto neither identify key or critical elements of all aspects nordelineate the scope of any or all aspects. Its sole purpose is topresent some concepts of one or more aspects in a simplified form as aprelude to the more detailed description that is presented later.

In an aspect of the disclosure, a method, a computer-readable medium,and an apparatus are provided. The apparatus may be a UE. The UEmeasures, at a first time point, a first set of reference signals todetermine a first set of values corresponding to a set of CSIparameters. The UE determines value differences between the first set ofvalues and a set of reference values corresponding to the set of CSIparameters. The UE sends a first CSI report including variationindicators indicating the value differences.

To the accomplishment of the foregoing and related ends, the one or moreaspects comprise the features hereinafter fully described andparticularly pointed out in the claims. The following description andthe annexed drawings set forth in detail certain illustrative featuresof the one or more aspects. These features are indicative, however, ofbut a few of the various ways in which the principles of various aspectsmay be employed, and this description is intended to include all suchaspects and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an example of a wireless communicationssystem and an access network.

FIG. 2 is a diagram illustrating a base station in communication with aUE in an access network.

FIG. 3 illustrates an example logical architecture of a distributedaccess network.

FIG. 4 illustrates an example physical architecture of a distributedaccess network.

FIG. 5 is a diagram showing an example of a DL-centric slot.

FIG. 6 is a diagram showing an example of an UL-centric slot.

FIG. 7 is a diagram illustrating CSI reporting from a UE to a basestation.

FIG. 8 is another diagram illustrating CSI reporting from a UE to a basestation.

FIG. 9 is a diagram illustrating a technique for CSI reporting.

FIG. 10 is a flow chart of a method (process) for performing CSIreporting.

FIG. 11 is a diagram illustrating an example of a hardwareimplementation for an apparatus employing a processing system.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appendeddrawings is intended as a description of various configurations and isnot intended to represent the only configurations in which the conceptsdescribed herein may be practiced. The detailed description includesspecific details for the purpose of providing a thorough understandingof various concepts. However, it will be apparent to those skilled inthe art that these concepts may be practiced without these specificdetails. In some instances, well known structures and components areshown in block diagram form in order to avoid obscuring such concepts.

Several aspects of telecommunications systems will now be presented withreference to various apparatus and methods. These apparatus and methodswill be described in the following detailed description and illustratedin the accompanying drawings by various blocks, components, circuits,processes, algorithms, etc. (collectively referred to as “elements”).These elements may be implemented using electronic hardware, computersoftware, or any combination thereof. Whether such elements areimplemented as hardware or software depends upon the particularapplication and design constraints imposed on the overall system.

By way of example, an element, or any portion of an element, or anycombination of elements may be implemented as a “processing system” thatincludes one or more processors. Examples of processors includemicroprocessors, microcontrollers, graphics processing units (GPUs),central processing units (CPUs), application processors, digital signalprocessors (DSPs), reduced instruction set computing (RISC) processors,systems on a chip (SoC), baseband processors, field programmable gatearrays (FPGAs), programmable logic devices (PLDs), state machines, gatedlogic, discrete hardware circuits, and other suitable hardwareconfigured to perform the various functionality described throughoutthis disclosure. One or more processors in the processing system mayexecute software. Software shall be construed broadly to meaninstructions, instruction sets, code, code segments, program code,programs, subprograms, software components, applications, softwareapplications, software packages, routines, subroutines, objects,executables, threads of execution, procedures, functions, etc., whetherreferred to as software, firmware, middleware, microcode, hardwaredescription language, or otherwise.

Accordingly, in one or more example aspects, the functions described maybe implemented in hardware, software, or any combination thereof. Ifimplemented in software, the functions may be stored on or encoded asone or more instructions or code on a computer-readable medium.Computer-readable media includes computer storage media. Storage mediamay be any available media that can be accessed by a computer. By way ofexample, and not limitation, such computer-readable media can comprise arandom-access memory (RAM), a read-only memory (ROM), an electricallyerasable programmable ROM (EEPROM), optical disk storage, magnetic diskstorage, other magnetic storage devices, combinations of theaforementioned types of computer-readable media, or any other mediumthat can be used to store computer executable code in the form ofinstructions or data structures that can be accessed by a computer.

FIG. 1 is a diagram illustrating an example of a wireless communicationssystem and an access network 100. The wireless communications system(also referred to as a wireless wide area network (WWAN)) includes basestations 102, UEs 104, an Evolved Packet Core (EPC) 160, and anothercore network 190 (e.g., a 5G Core (5GC)). The base stations 102 mayinclude macrocells (high power cellular base station) and/or small cells(low power cellular base station). The macrocells include base stations.The small cells include femtocells, picocells, and microcells.

The base stations 102 configured for 4G LTE (collectively referred to asEvolved Universal Mobile Telecommunications System (UMTS) TerrestrialRadio Access Network (E-UTRAN)) may interface with the EPC 160 throughbackhaul links 132 (e.g., SI interface). The base stations 102configured for 5G NR (collectively referred to as Next Generation RAN(NG-RAN)) may interface with core network 190 through backhaul links184. In addition to other functions, the base stations 102 may performone or more of the following functions: transfer of user data, radiochannel ciphering and deciphering, integrity protection, headercompression, mobility control functions (e.g., handover, dualconnectivity), inter cell interference coordination, connection setupand release, load balancing, distribution for non-access stratum (NAS)messages, NAS node selection, synchronization, radio access network(RAN) sharing, multimedia broadcast multicast service (MBMS), subscriberand equipment trace, RAN information management (RIM), paging,positioning, and delivery of warning messages. The base stations 102 maycommunicate directly or indirectly (e.g., through the EPC 160 or corenetwork 190) with each other over backhaul links 134 (e.g., X2interface). The backhaul links 134 may be wired or wireless.

The base stations 102 may wirelessly communicate with the UEs 104. Eachof the base stations 102 may provide communication coverage for arespective geographic coverage area 110. There may be overlappinggeographic coverage areas 110. For example, the small cell 102′ may havea coverage area 110′ that overlaps the coverage area 110 of one or moremacro base stations 102. A network that includes both small cell andmacrocells may be known as a heterogeneous network. A heterogeneousnetwork may also include Home Evolved Node Bs (eNBs) (HeNBs), which mayprovide service to a restricted group known as a closed subscriber group(CSG). The communication links 120 between the base stations 102 and theUEs 104 may include uplink (UL) (also referred to as reverse link)transmissions from a UE 104 to a base station 102 and/or downlink (DL)(also referred to as forward link) transmissions from a base station 102to a UE 104. The communication links 120 may use multiple-input andmultiple-output (MIMO) antenna technology, including spatialmultiplexing, beamforming, and/or transmit diversity. The communicationlinks may be through one or more carriers. The base stations 102/UEs 104may use spectrum up to X MHz (e.g., 5, 10, 15, 20, 100, 400, etc. MHz)bandwidth per carrier allocated in a carrier aggregation of up to atotal of Yx MHz (x component carriers) used for transmission in eachdirection. The carriers may or may not be adjacent to each other.Allocation of carriers may be asymmetric with respect to DL and UL(e.g., more or fewer carriers may be allocated for DL than for UL). Thecomponent carriers may include a primary component carrier and one ormore secondary component carriers. A primary component carrier may bereferred to as a primary cell (PCell) and a secondary component carriermay be referred to as a secondary cell (SCell).

Certain UEs 104 may communicate with each other using device-to-device(D2D) communication link 158. The D2D communication link 158 may use theDL/UL WWAN spectrum. The D2D communication link 158 may use one or moresidelink channels, such as a physical sidelink broadcast channel(PSBCH), a physical sidelink discovery channel (PSDCH), a physicalsidelink shared channel (PSSCH), and a physical sidelink control channel(PSCCH). D2D communication may be through a variety of wireless D2Dcommunications systems, such as for example, FlashLinQ, WiMedia,Bluetooth, ZigBee, Wi-Fi based on the IEEE 802.11 standard, LTE, or NR.

The wireless communications system may further include a Wi-Fi accesspoint (AP) 150 in communication with Wi-Fi stations (STAs) 152 viacommunication links 154 in a 5 GHz unlicensed frequency spectrum. Whencommunicating in an unlicensed frequency spectrum, the STAs 152/AP 150may perform a clear channel assessment (CCA) prior to communicating inorder to determine whether the channel is available.

The small cell 102′ may operate in a licensed and/or an unlicensedfrequency spectrum. When operating in an unlicensed frequency spectrum,the small cell 102′ may employ NR and use the same 5 GHz unlicensedfrequency spectrum as used by the Wi-Fi AP 150. The small cell 102′,employing NR in an unlicensed frequency spectrum, may boost coverage toand/or increase capacity of the access network.

A base station 102, whether a small cell 102′ or a large cell (e.g.,macro base station), may include an eNB, gNodeB (gNB), or another typeof base station. Some base stations, such as gNB 180 may operate in atraditional sub 6 GHz spectrum, in millimeter wave (mmW) frequencies,and/or near mmW frequencies in communication with the UE 104 When thegNB 180 operates in mmW or near mmW frequencies, the gNB 180 may bereferred to as an mmW base station. Extremely high frequency (EHF) ispart of the RF in the electromagnetic spectrum. EHF has a range of 30GHz to 300 GHz and a wavelength between 1 millimeter and 10 millimeters.Radio waves in the band may be referred to as a millimeter wave. NearmmW may extend down to a frequency of 3 GHz with a wavelength of 100millimeters. The super high frequency (SHF) band extends between 3 GHzand 30 GHz, also referred to as centimeter wave. Communications usingthe mmW/near mmW radio frequency band (e.g., 3 GHz-300 GHz) hasextremely high path loss and a short range. The mmW base station 180 mayutilize beamforming 182 with the UE 104 to compensate for the extremelyhigh path loss and short range.

The base station 180 may transmit a beamformed signal to the UE 104 inone or more transmit directions 108 a. The UE 104 may receive thebeamformed signal from the base station 180 in one or more receivedirections 108 b. The UE 104 may also transmit a beamformed signal tothe base station 180 in one or more transmit directions. The basestation 180 may receive the beamformed signal from the UE 104 in one ormore receive directions. The base station 180/UE 104 may perform beamtraining to determine the best receive and transmit directions for eachof the base station 180/UE 104. The transmit and receive directions forthe base station 180 may or may not be the same. The transmit andreceive directions for the UE 104 may or may not be the same.

The EPC 160 may include a Mobility Management Entity (MME) 162, otherMMEs 164, a Serving Gateway 166, a Multimedia Broadcast MulticastService (MBMS) Gateway 168, a Broadcast Multicast Service Center (BM-SC)170, and a Packet Data Network (PDN) Gateway 172. The MME 162 may be incommunication with a Home Subscriber Server (HSS) 174. The MME 162 isthe control node that processes the signaling between the UEs 104 andthe EPC 160. Generally, the MME 162 provides bearer and connectionmanagement. All user Internet protocol (IP) packets are transferredthrough the Serving Gateway 166, which itself is connected to the PDNGateway 172. The PDN Gateway 172 provides UE IP address allocation aswell as other functions. The PDN Gateway 172 and the BM-SC 170 areconnected to the IP Services 176. The IP Services 176 may include theInternet, an intranet, an IP Multimedia Subsystem (IMS), a PS StreamingService, and/or other IP services. The BM-SC 170 may provide functionsfor MBMS user service provisioning and delivery. The BM-SC 170 may serveas an entry point for content provider MBMS transmission, may be used toauthorize and initiate MBMS Bearer Services within a public land mobilenetwork (PLMN), and may be used to schedule MBMS transmissions. The MBMSGateway 168 may be used to distribute MBMS traffic to the base stations102 belonging to a Multicast Broadcast Single Frequency Network (MBSFN)area broadcasting a particular service, and may be responsible forsession management (start/stop) and for collecting eMBMS relatedcharging information.

The core network 190 may include a Access and Mobility ManagementFunction (AMF) 192, other AMFs 193, a location management function (LMF)198, a Session Management Function (SMF) 194, and a User Plane Function(UPF) 195. The AMF 192 may be in communication with a Unified DataManagement (UDM) 196. The AMF 192 is the control node that processes thesignaling between the UEs 104 and the core network 190. Generally, theSMF 194 provides QoS flow and session management. All user Internetprotocol (IP) packets are transferred through the UPF 195. The UPF 195provides UE IP address allocation as well as other functions. The UPF195 is connected to the IP Services 197. The IP Services 197 may includethe Internet, an intranet, an IP Multimedia Subsystem (IMS), a PSStreaming Service, and/or other IP services.

The base station may also be referred to as a gNB, Node B, evolved NodeB (eNB), an access point, a base transceiver station, a radio basestation, a radio transceiver, a transceiver function, a basic serviceset (BSS), an extended service set (ESS), a transmit reception point(TRP), or some other suitable terminology. The base station 102 providesan access point to the EPC 160 or core network 190 for a UE 104 Examplesof UEs 104 include a cellular phone, a smart phone, a session initiationprotocol (SIP) phone, a laptop, a personal digital assistant (PDA), asatellite radio, a global positioning system, a multimedia device, avideo device, a digital audio player (e.g., MP3 player), a camera, agame console, a tablet, a smart device, a wearable device, a vehicle, anelectric meter, a gas pump, a large or small kitchen appliance, ahealthcare device, an implant, a sensor/actuator, a display, or anyother similar functioning device. Some of the UEs 104 may be referred toas IoT devices (e.g., parking meter, gas pump, toaster, vehicles, heartmonitor, etc.). The UE 104 may also be referred to as a station, amobile station, a subscriber station, a mobile unit, a subscriber unit,a wireless unit, a remote unit, a mobile device, a wireless device, awireless communications device, a remote device, a mobile subscriberstation, an access terminal, a mobile terminal, a wireless terminal, aremote terminal, a handset, a user agent, a mobile client, a client, orsome other suitable terminology.

Although the present disclosure may reference 5G New Radio (NR), thepresent disclosure may be applicable to other similar areas, such asLTE, LTE-Advanced (LTE-A), Code Division Multiple Access (CDMA), GlobalSystem for Mobile communications (GSM), or other wireless/radio accesstechnologies.

FIG. 2 is a block diagram of a base station 210 in communication with aUE 250 in an access network. In the DL, IP packets from the EPC 160 maybe provided to a controller/processor 275. The controller/processor 275implements layer 3 and layer 2 functionality. Layer 3 includes a radioresource control (RRC) layer, and layer 2 includes a packet dataconvergence protocol (PDCP) layer, a radio link control (RLC) layer, anda medium access control (MAC) layer. The controller/processor 275provides RRC layer functionality associated with broadcasting of systeminformation (e.g., MIB, SIBs), RRC connection control (e.g., RRCconnection paging, RRC connection establishment, RRC connectionmodification, and RRC connection release), inter radio access technology(RAT) mobility, and measurement configuration for UE measurementreporting; PDCP layer functionality associated with headercompression/decompression, security (ciphering, deciphering, integrityprotection, integrity verification), and handover support functions; RLClayer functionality associated with the transfer of upper layer packetdata units (PDUs), error correction through ARQ, concatenation,segmentation, and reassembly of RLC service data units (SDUs),re-segmentation of RLC data PDUs, and reordering of RLC data PDUs; andMAC layer functionality associated with mapping between logical channelsand transport channels, multiplexing of MAC SDUs onto transport blocks(TBs), demultiplexing of MAC SDUs from TBs, scheduling informationreporting, error correction through HARQ, priority handling, and logicalchannel prioritization.

The transmit (TX) processor 216 and the receive (RX) processor 270implement layer 1 functionality associated with various signalprocessing functions. Layer 1, which includes a physical (PHY) layer,may include error detection on the transport channels, forward errorcorrection (FEC) coding/decoding of the transport channels,interleaving, rate matching, mapping onto physical channels,modulation/demodulation of physical channels, and MIMO antennaprocessing. The TX processor 216 handles mapping to signalconstellations based on various modulation schemes (e.g., binaryphase-shift keying (BPSK), quadrature phase-shift keying (QPSK),M-phase-shift keying (M-PSK), M-quadrature amplitude modulation (M-QAM).The coded and modulated symbols may then be split into parallel streams.Each stream may then be mapped to an OFDM subcarrier, multiplexed with areference signal (e.g., pilot) in the time and/or frequency domain, andthen combined together using an Inverse Fast Fourier Transform (IFFT) toproduce a physical channel carrying a time domain OFDM symbol stream.The OFDM stream is spatially precoded to produce multiple spatialstreams. Channel estimates from a channel estimator 274 may be used todetermine the coding and modulation scheme, as well as for spatialprocessing. The channel estimate may be derived from a reference signaland/or channel condition feedback transmitted by the UE 250. Eachspatial stream may then be provided to a different antenna 220 via aseparate transmitter 218TX. Each transmitter 218TX may modulate an RFcarrier with a respective spatial stream for transmission.

At the UE 250, each receiver 254RX receives a signal through itsrespective antenna 252. Each receiver 254RX recovers informationmodulated onto an RF carrier and provides the information to the receive(RX) processor 256. The TX processor 268 and the RX processor 256implement layer 1 functionality associated with various signalprocessing functions. The RX processor 256 may perform spatialprocessing on the information to recover any spatial streams destinedfor the UE 250. If multiple spatial streams are destined for the UE 250,they may be combined by the RX processor 256 into a single OFDM symbolstream. The RX processor 256 then converts the OFDM symbol stream fromthe time-domain to the frequency domain using a Fast Fourier Transform(FFT). The frequency domain signal comprises a separate OFDM symbolstream for each subcarrier of the OFDM signal. The symbols on eachsubcarrier, and the reference signal, are recovered and demodulated bydetermining the most likely signal constellation points transmitted bythe base station 210. These soft decisions may be based on channelestimates computed by the channel estimator 258. The soft decisions arethen decoded and deinterleaved to recover the data and control signalsthat were originally transmitted by the base station 210 on the physicalchannel. The data and control signals are then provided to thecontroller/processor 259, which implements layer 3 and layer 2functionality.

The controller/processor 259 can be associated with a memory 260 thatstores program codes and data. The memory 260 may be referred to as acomputer-readable medium. In the UL, the controller/processor 259provides demultiplexing between transport and logical channels, packetreassembly, deciphering, header decompression, and control signalprocessing to recover IP packets from the EPC 160. Thecontroller/processor 259 is also responsible for error detection usingan ACK and/or NACK protocol to support HARQ operations.

Similar to the functionality described in connection with the DLtransmission by the base station 210, the controller/processor 259provides RRC layer functionality associated with system information(e.g., MIB, SIBs) acquisition, RRC connections, and measurementreporting; PDCP layer functionality associated with headercompression/decompression, and security (ciphering, deciphering,integrity protection, integrity verification); RLC layer functionalityassociated with the transfer of upper layer PDUs, error correctionthrough ARQ, concatenation, segmentation, and reassembly of RLC SDUs,re-segmentation of RLC data PDUs, and reordering of RLC data PDUs; andMAC layer functionality associated with mapping between logical channelsand transport channels, multiplexing of MAC SDUs onto TBs,demultiplexing of MAC SDUs from TBs, scheduling information reporting,error correction through HARQ, priority handling, and logical channelprioritization.

Channel estimates derived by a channel estimator 258 from a referencesignal or feedback transmitted by the base station 210 may be used bythe TX processor 268 to select the appropriate coding and modulationschemes, and to facilitate spatial processing. The spatial streamsgenerated by the TX processor 268 may be provided to different antenna252 via separate transmitters 254TX. Each transmitter 254TX may modulatean RF carrier with a respective spatial stream for transmission. The ULtransmission is processed at the base station 210 in a manner similar tothat described in connection with the receiver function at the UE 250.Each receiver 218RX receives a signal through its respective antenna220. Each receiver 218RX recovers information modulated onto an RFcarrier and provides the information to a RX processor 270.

The controller/processor 275 can be associated with a memory 276 thatstores program codes and data. The memory 276 may be referred to as acomputer-readable medium. In the UL, the controller/processor 275provides demultiplexing between transport and logical channels, packetreassembly, deciphering, header decompression, control signal processingto recover IP packets from the UE 250. IP packets from thecontroller/processor 275 may be provided to the EPC 160. Thecontroller/processor 275 is also responsible for error detection usingan ACK and/or NACK protocol to support HARQ operations.

New radio (NR) may refer to radios configured to operate according to anew air interface (e.g., other than Orthogonal Frequency DivisionalMultiple Access (OFDMA)-based air interfaces) or fixed transport layer(e.g., other than Internet Protocol (IP)). NR may utilize OFDM with acyclic prefix (CP) on the uplink and downlink and may include supportfor half-duplex operation using time division duplexing (TDD). NR mayinclude Enhanced Mobile Broadband (eMBB) service targeting widebandwidth (e.g. 80 MHz beyond), millimeter wave (mmW) targeting highcarrier frequency (e.g. 60 GHz), massive MTC (mMTC) targetingnon-backward compatible MTC techniques, and/or mission criticaltargeting ultra-reliable low latency communications (URLLC) service.

A single component carrier bandwidth of 100 MHz may be supported. In oneexample, NR resource blocks (RBs) may span 12 sub-carriers with asub-carrier bandwidth of 60 kHz over a 0.25 ms duration or a bandwidthof 30 kHz over a 0.5 ms duration (similarly, 50 MHz BW for 15 kHz SCSover a 1 ms duration). Each radio frame may consist of 10 subframes (10,20, 40 or 80 NR slots) with a length of 10 ms. Each slot may indicate alink direction (i.e., DL or UL) for data transmission and the linkdirection for each slot may be dynamically switched. Each slot mayinclude DL/UL data as well as DL/UL control data. UL and DL slots for NRmay be as described in more detail below with respect to FIGS. 5 and 6.

The NR RAN may include a central unit (CU) and distributed units (DUs).A NR BS (e.g., gNB, 5G Node B, Node B, transmission reception point(TRP), access point (AP)) may correspond to one or multiple BSs. NRcells can be configured as access cells (ACells) or data only cells(DCells). For example, the RAN (e.g., a central unit or distributedunit) can configure the cells. DCells may be cells used for carrieraggregation or dual connectivity and may not be used for initial access,cell selection/reselection, or handover. In some cases DCells may nottransmit synchronization signals (SS) in some cases DCells may transmitSS. NR BSs may transmit downlink signals to UEs indicating the celltype. Based on the cell type indication, the UE may communicate with theNR BS. For example, the UE may determine NR BSs to consider for cellselection, access, handover, and/or measurement based on the indicatedcell type.

FIG. 3 illustrates an example logical architecture of a distributed RAN300, according to aspects of the present disclosure. A 5G access node306 may include an access node controller (ANC) 302. The ANC may be acentral unit (CU) of the distributed RAN. The backhaul interface to thenext generation core network (NG-CN) 304 may terminate at the ANC. Thebackhaul interface to neighboring next generation access nodes (NG-ANs)310 may terminate at the ANC. The ANC may include one or more TRPs 308(which may also be referred to as BSs, NR BSs, Node Bs, 5G NBs, APs, orsome other term). As described above, a TRP may be used interchangeablywith “cell”.

The TRPs 308 may be a distributed unit (DU). The TRPs may be connectedto one ANC (ANC 302 ) or more than one ANC (not illustrated). Forexample, for RAN sharing, radio as a service (RaaS), and servicespecific ANC deployments, the TRP may be connected to more than one ANC.A TRP may include one or more antenna ports. The TRPs may be configuredto individually (e.g., dynamic selection) or jointly (e.g., jointtransmission) serve traffic to a UE.

The local architecture of the distributed RAN 300 may be used toillustrate fronthaul definition. The architecture may be defined thatsupport fronthauling solutions across different deployment types. Forexample, the architecture may be based on transmit network capabilities(e.g., bandwidth, latency, and/or jitter). The architecture may sharefeatures and/or components with LTE. According to aspects, the nextgeneration AN (NG-AN) 310 may support dual connectivity with NR. TheNG-AN may share a common fronthaul for LTE and NR.

The architecture may enable cooperation between and among TRPs 308. Forexample, cooperation may be preset within a TRP and/or across TRPs viathe ANC 302. According to aspects, no inter-TRP interface may beneeded/present.

According to aspects, a dynamic configuration of split logical functionsmay be present within the architecture of the distributed RAN 300. ThePDCP, RLC, MAC protocol may be adaptably placed at the ANC or TRP.

FIG. 4 illustrates an example physical architecture of a distributed RAN400, according to aspects of the present disclosure. A centralized corenetwork unit (C-CU) 402 may host core network functions. The C-CU may becentrally deployed. C-CU functionality may be offloaded (e.g., toadvanced wireless services (AWS)), in an effort to handle peak capacity.A centralized RAN unit (C-RU) 404 may host one or more ANC functions.Optionally, the C-RU may host core network functions locally. The C- RUmay have distributed deployment. The C-RU may be closer to the networkedge. A distributed unit (DU) 406 may host one or more TRPs. The DU maybe located at edges of the network with radio frequency (RF)functionality.

FIG. 5 is a diagram 500 showing an example of a DL-centric slot. TheDL-centric slot may include a control portion 502. The control portion502 may exist in the initial or beginning portion of the DL-centricslot. The control portion 502 may include various scheduling informationand/or control information corresponding to various portions of theDL-centric slot. In some configurations, the control portion 502 may bea physical DL control channel (PDCCH), as indicated in FIG. 5. TheDL-centric slot may also include a DL data portion 504. The DL dataportion 504 may sometimes be referred to as the payload of theDL-centric slot. The DL data portion 504 may include the communicationresources utilized to communicate DL data from the scheduling entity(e.g., UE or BS) to the subordinate entity (e.g., UE). In someconfigurations, the DL data portion 504 may be a physical DL sharedchannel (PDSCH).

The DL-centric slot may also include a common UL portion 506. The commonUL portion 506 may sometimes be referred to as an UL burst, a common ULburst, and/or various other suitable terms. The common UL portion 506may include feedback information corresponding to various other portionsof the DL-centric slot. For example, the common UL portion 506 mayinclude feedback information corresponding to the control portion 502.Non-limiting examples of feedback information may include an ACK signal,a NACK signal, a HARQ indicator, and/or various other suitable types ofinformation. The common UL portion 506 may include additional oralternative information, such as information pertaining to random accesschannel (RACH) procedures, scheduling requests (SRs), and various othersuitable types of information.

As illustrated in FIG. 5, the end of the DL data portion 504 may beseparated in time from the beginning of the common UL portion 506. Thistime separation may sometimes be referred to as a gap, a guard period, aguard interval, and/or various other suitable terms. This separationprovides time for the switch-over from DL communication (e.g., receptionoperation by the subordinate entity (e.g., UE)) to UL communication(e.g., transmission by the subordinate entity (e.g., UE)). One ofordinary skill in the art will understand that the foregoing is merelyone example of a DL-centric slot and alternative structures havingsimilar features may exist without necessarily deviating from theaspects described herein.

FIG. 6 is a diagram 600 showing an example of an UL-centric slot. TheUL-centric slot may include a control portion 602. The control portion602 may exist in the initial or beginning portion of the UL-centricslot. The control portion 602 in FIG. 6 may be similar to the controlportion 502 described above with reference to FIG. 5. The UL-centricslot may also include an UL data portion 604. The UL data portion 604may sometimes be referred to as the pay load of the UL-centric slot. TheUL portion may refer to the communication resources utilized tocommunicate UL data from the subordinate entity (e.g., UE) to thescheduling entity (e.g., UE or BS). In some configurations, the controlportion 602 may be a physical DL control channel (PDCCH).

As illustrated in FIG. 6, the end of the control portion 602 may beseparated in time from the beginning of the UL data portion 604. Thistime separation may sometimes be referred to as a gap, guard period,guard interval, and/or various other suitable terms. This separationprovides time for the switch-over from DL communication (e.g., receptionoperation by the scheduling entity) to UL communication (e.g.,transmission by the scheduling entity). The UL-centric slot may alsoinclude a common UL portion 606. The common UL portion 606 in FIG. 6 maybe similar to the common UL portion 506 described above with referenceto FIG. 5. The common UL portion 606 may additionally or alternativelyinclude information pertaining to channel quality indicator (CQI),sounding reference signals (SRSs), and various other suitable types ofinformation. One of ordinary skill in the art will understand that theforegoing is merely one example of an UL-centric slot and alternativestructures having similar features may exist without necessarilydeviating from the aspects described herein.

In some circumstances, two or more subordinate entities (e.g., UEs) maycommunicate with each other using sidelink signals. Real-worldapplications of such sidelink communications may include public safety,proximity services, UE-to-network relaying, vehicle-to-vehicle (V2V)communications, Internet of Everything (IoE) communications, IoTcommunications, mission-critical mesh, and/or various other suitableapplications. Generally, a sidelink signal may refer to a signalcommunicated from one subordinate entity (e.g., UE1) to anothersubordinate entity (e.g., UE2) without relaying that communicationthrough the scheduling entity (e.g., UE or BS), even though thescheduling entity may be utilized for scheduling and/or controlpurposes. In some examples, the sidelink signals may be communicatedusing a licensed spectrum (unlike wireless local area networks, whichtypically use an unlicensed spectrum).

FIG. 7 is a diagram 700 illustrating CSI reporting from a UE to a basestation. A base station 702 and a UE 704 communicate on a channel 710.The base station 702 may transmit spatial beams 740 on the channel 710.Channel properties of the channel 710 (i.e., a wireless communicationlink) is referred to as channel state information 714 This informationdescribes how a signal propagates from the transmitter at the basestation 702 to the receiver at the UE 704 and represents the combinedeffect of scattering, multipath fading, signal power attenuation withdistance, etc. The knowledge of the channel state information 714 at thetransmitter and/or the receiver makes it possible to adapt datatransmission to current channel conditions, which is crucial forachieving reliable and robust communication with high data rates inmulti-antenna systems. The channel state information 714 is oftenrequired to be estimated at the receiver, and usually quantized and fedback to the transmitter.

The time and frequency resources that can be used by the UE 704 toreport the channel state information 714 are controlled by the basestation 702. The channel state information 714 may include CQI, PMI,CSI-RS resource indicator (CRI), SS block resource indicator, layerindication (LI), rank indicator (RI), and/or and L1-RSRP measurements.For CQI, PMI, CRI, LI, RI, L1-RSRP, the UE 704 may be configured via RRCsignaling with more than one CSI-reportConfig reporting settings,CSI-ResourceConfig resource settings, and one or two lists of triggerstates, indicating the resource set IDs for channel and optionally forinterference measurement. Each trigger state contains an associatedCSI-ReportConfig.

The UE 704 measures the spatial channel between itself and the servingbase station using the CSI- RS transmitted from the base station 702transmit antenna ports in order to generate a CSI report. The UE 704then calculates the CSI-related metrics and reports the CSI to the basestation 702. Using the reported CSIs from all UEs, the base station 702performs link adaptation and scheduling. The goal of CSI measurement andreporting is to obtain an approximation of the CSI. This can be achievedwhen the reported PMI accurately represents the dominant channeleigenvector(s), thereby enabling accurate beamforming.

The NR supports multiple types of spatial-resolution CSI, includingstandard-resolution (Type I) and high-resolution (Type II). Thelow-resolution CSI is targeted for SU-MIMO transmission since it relieson the UE receiver to suppress the inter-layer interference. This ispossible since the number of received layers is less than the number ofreceiver antennas for a given UE. For MU-MIMO transmission, the numberof received layers is typically larger than the number of receiveantennas for the UE. The base station exploits beamforming/precoding tosuppress inter-UE interference. Thus, a higher resolution CSI, capturingmore propagation paths of the channel, is needed to provide sufficientdegrees of freedom at the transmitter.

For high-spatial-resolution (Type II) CSI, feedback of two layers may besupported with a linear combination codebook. The codebook resolution issufficiently high to facilitate sufficiently accurate approximation ofthe downlink channel. In this scheme, the UE reports a PMI thatrepresents a linear combination of multiple beams. Both Type I CSI andType II CSI employ a dual-stage W=W₁W₂ codebook, where W₁ is a widebandprecoder representing selected spatial vector basis, and W₂ is a subbandprecoder representing further basis down-selection and/or co-phasing forType I CSI and linear combination coefficients corresponding to theselected spatial basis for Type II CSI, respectively.

In certain configurations, the channel 710 between the base station 702and the UE 704 has a rank R. The frequencies of the channel 710 can bedivided into a number of sub-bands or frequency units. The frequencyunits can be indexed from 1 to F_(total). The precoder W for rank r andfrequency unit indexed f can be written as

$W_{r,f} = {\begin{bmatrix}B & \\ & B\end{bmatrix}\underset{W_{r,f}^{(2)}}{\underset{︸}{\begin{bmatrix}{\overset{\sim}{w}}_{0,r,f} \\ \vdots \\{\overset{\sim}{w}}_{l,r,f} \\ \vdots \\{\overset{\sim}{w}}_{{L - 1},r,f} \\{\overset{\sim}{w}}_{L,r,f} \\ \vdots \\{\overset{\sim}{w}}_{{l + L},r,f} \\ \vdots \\{\overset{\sim}{w}}_{{{2L} - 1},r,f}\end{bmatrix}}}}$

where B=[b₁ . . . b_(l) . . . b_(L) ]. L is the number of basis beams742 per polarization; each b_(i) is a spatial beam selected in awideband fashion per polarization, where 1≤i≤L. In total, 2L spatialbeams are selected for two polarization. r is the spatial layer index,1≤r≤R; f is a frequency index (e.g., the subband index or PRB index),1≤f≤F_(total), where F_(total) is the total number of frequency units(sub-bands, PRBs etc.) over which the CSI feedback is applicable, e.g.,16 or 19.

In order to reduce feedback overhead for Type-II codebook, another“enhanced Type-II codebook” was introduced by compressing the CSI reportin frequency domain. The precoders for spatial layer r for all frequencyindices 1≤f≤N₃ in a segment can be written as:

$\begin{matrix}{\left\lbrack {W_{r,1}\cdots W_{r,F}} \right\rbrack = {\begin{bmatrix}{B} & \\ & B\end{bmatrix}\left\lbrack {w_{r,0}^{(2)}\cdots w_{r,{N_{3} - 1}}^{(2)}} \right\rbrack}} & \\{= {\begin{bmatrix}B & \\ & B\end{bmatrix}\begin{bmatrix}{\overset{\sim}{w}}_{0,r,0} & \cdots & {\overset{\sim}{w}}_{0,r,{N_{3} - 1}} \\ \vdots & \cdots & \vdots \\{\overset{\sim}{w}}_{l,r,0} & \cdots & {\overset{\sim}{w}}_{l,r,{N_{3} - 1}} \\ \vdots & \cdots & \vdots \\{\overset{\sim}{w}}_{{L - 1},r,0} & \cdots & {\overset{\sim}{w}}_{{L - 1},r,{N_{3} - 1}} \\{\overset{\sim}{w}}_{L,r,0} & \cdots & {\overset{\sim}{w}}_{L,r,{N_{3} - 1}} \\ \vdots & \cdots & \vdots \\{\overset{\sim}{w}}_{{l + L},r,0} & \cdots & {\overset{\sim}{w}}_{{l + L},r,{N_{3} - 1}} \\ \vdots & \cdots & \vdots \\{\overset{\sim}{w}}_{{{2L} - 1},r,0} & \cdots & {\overset{\sim}{w}}_{{{2L} - 1},r,{N_{3} - 1}}\end{bmatrix}}} & \\{= \text{}{\begin{bmatrix}B & \\ & B\end{bmatrix}{\underset{W_{2}}{\underset{︸}{\begin{bmatrix}w_{0,r,0} & \cdots & w_{0,r,{N_{3} - 1}} \\ \vdots & \cdots & \vdots \\w_{l,r,0} & \cdots & w_{l,r,{N_{3} - 1}} \\ \vdots & \cdots & \vdots \\w_{{L - 1},r,0} & \cdots & w_{{L - 1},r,{N_{3} - 1}} \\w_{L,r,0} & \cdots & w_{L,r,{N_{3} - 1}} \\ \vdots & \cdots & \vdots \\w_{{l + L},r,0} & \cdots & w_{{l + L},r,{N_{3} - 1}} \\ \vdots & \cdots & \vdots \\w_{{{2L} - 1},r,0} & \cdots & w_{{{2L} - 1},r,{N_{3} - 1}}\end{bmatrix}}}\begin{bmatrix}f_{0}^{H} \\ \vdots \\f_{N_{3} - 1}^{H}\end{bmatrix}}}} & \\{\approx \text{}{\begin{bmatrix}B & \\ & B\end{bmatrix}\underset{{\overset{\sim}{W}}_{2}}{\underset{︸}{\begin{bmatrix}w_{0,r,{\overset{\_}{k}}_{0}} & \cdots & w_{0,r,{\overset{\_}{k}}_{M - 1}} \\ \vdots & \cdots & \vdots \\w_{l,r,{\overset{\_}{k}}_{0}} & \cdots & w_{l,r,{\overset{\_}{k}}_{M - 1}} \\ \vdots & \cdots & \vdots \\w_{{L - 1},r,{\overset{\_}{k}}_{0}} & \cdots & w_{{L - 1},r,{\overset{\_}{k}}_{M - 1}} \\w_{L,r,{\overset{\_}{k}}_{0}} & \cdots & {\overset{\sim}{w}}_{L,r,{\overset{\_}{k}}_{M - 1}} \\ \vdots & \cdots & \vdots \\w_{{l + L},r,{\overset{\_}{k}}_{0}} & \cdots & w_{{l + L},r,{\overset{\_}{k}}_{M - 1}} \\ \vdots & \cdots & \vdots \\w_{{{2L} - 1},r,{\overset{\_}{k}}_{0}} & \cdots & w_{{{2L} - 1},r,{\overset{\_}{k}}_{M - 1}}\end{bmatrix}}}\underset{{\overset{\sim}{W}}_{f}}{\underset{︸}{\begin{bmatrix}f_{{\overset{\_}{k}}_{0}}^{H} \\ \vdots \\f_{{\overset{\_}{k}}_{M - 1}}^{H}\end{bmatrix}}}}} & \end{matrix}$ and ${f_{d} = \begin{bmatrix}e^{{j \cdot 2}\pi\frac{{m_{d} \cdot 0 \cdot O_{3}} + o_{3}}{N_{3}O_{3}}} \\e^{{j \cdot 2}\pi\frac{{m_{d} \cdot 1 \cdot O_{3}} + o_{3}}{N_{3}O_{3}}} \\ \vdots \\e^{{j \cdot 2}\pi\frac{{m_{d} \cdot {({N_{3} - 1})} \cdot O_{3}} + o_{3}}{N_{3}O_{3}}}\end{bmatrix}},$

where N₃ is the number of sub-bands (or frequency bins) for CSI feedbackor equally the maximum number of delay taps in the time domainformulation, and O₃ is an oversampling factor. And M delay taps (or FDcomponents) are used in the approximation; and O₃'s role is bestunderstood in the time domain formulation as it provides a finer timingunit for delay taps through o₃,0≤o₃≤O³⁻¹.

FIG. 8 is a diagram 800 illustrating CSI reporting from the UE 704 tothe base station 702. The channel state of the UE 704 can be defined bya set of CSI parameters, the values of which specify the channel state.The CQI, PMI, CRI, LI, RI, L1-RSRP, etc. described supra can be used toindicate the values of the CSI parameters. Further, the UE 704 may sendone or more CSI reports to the base station 702. Each CSI report maycontain one or more of the CQI, PMI, CRI, LI, RI, L1-RSRP, etc., thusinforming the base station 702 the channel state at the UE 704.

In this example, according to the techniques described infra, at a timepoint t₁, the UE 704 perform a set of CSI measurements and then generatea full CSI report A based on the measurements. Subsequently, at a timepoint t₁′, the UE 704 sends the full CSI report A to the base station702. Similarly, the UE 704 performs a second set of measurements at atime point t₂ and may send a corresponding differential CSI report B ata time point t₂′; the UE 704 performs a third set of measurements at atime point t₃ and may send a corresponding differential CSI report C ata time point t₃′.

More specifically, in a first technique, the UE 704 and the base station702 share a prediction model that estimates the values of the CSIparameters. The UE 704 may generate the prediction model and then sendthe prediction model to the base station 702. Alternatively, network mayconfigure the prediction model for both the base station 702 and the UE704. In this example, there are Q CSI parameters v₁, v₂ , . . . , v_(Q),which can be vectorized into a vector V:

$\begin{bmatrix}v_{1} \\v_{2} \\v_{3} \\ \vdots \\v_{Q}\end{bmatrix}$

Further, V(s) denotes the values of the Q CSI parameters v₁, v₂ , . . ., v_(Q) at a s^(th) time point at which a set of CSI measurements areperformed. s is an integer greater than 1. The prediction model can bewritten as:

${\overset{\_}{V}(s)} = {\overset{K}{\sum\limits_{i = 1}}{a_{s - i}{V\left( {s - i} \right)}}}$

Vare predicted values. V are known values. K is an integer greater than0 and less than s. a_(s−i) is the coefficient corresponding to V(s−i).In one example, where s=4, K=2, the prediction model is:

V (4)=a ₃ V(3)+a ₂ V(2)

As described supra, the precoding matrix W can be written as W=W₁×W₂. Incertain circumstances, the values of W₁ may change at a slower rate thanthe values of W₂ do. For example, in a given time duration, thepercentage changes of the values of W₂ may be larger than the percentagechanges of the values of W₁. Accordingly, the UE 704 may report W₁ andW₂ separately, and may report W₂ more frequently than reporting W₁.

In one example, the precoding matrix W₂ described supra can berepresented by V: v₁ may be {tilde over (w)}_(0,r,0), v₂ may be {tildeover (w)}_(1,r,0), and so on. W₂(t) denotes the values of W₂ at a timepoint t. W₂ may be selected from Type-I Codebook, Type-II Codebook,Enhanced Type-II Codebook, etc. At t₁ , the UE 704 performs a set of CSImeasurements and determines W₂(t₁). Accordingly, the UE 704 can generateV(t₁). At t₁′, the UE 704 sends a full CSI report A, which includesindicators (e.g., PMIs) indicating the values of W₂(t₁). The basestation 702 receives the indicators and accordingly can derive thevalues of W₂(t₁). As such, the base station 702 can generate V(t₁).

Subsequently, at t₂, the UE 704 performs another set of CSI measurementsand determines the values of W₂(t₂). The UE 704 can generate V(t₂).Further, in this example, K is 2. Using the prediction model(i.e.,V(2)=a₁V(1)), the UE 704 can calculate V(t₂) based on V(t₁). TheUE 704 can further calculate a difference between V(t₂) and V(t₂):

The UE 704 can determine elements of ΔV(t₂) that are not zero andgenerate variation indicators indicating those non-zero elements ofΔV(t₂). Subsequently, at t₂′, the UE 704 sends to the base station 702 adifferential CSI report B containing the variation indicators instead ofa full CSI report. As such, in certain circumstances where the number ofnon-zero elements are limited and variation of the elements of ΔV(t₂) isalso limited, the information bits used to carry the variationindicators may be substantial less than the information bits needed tocarry PMIs indicating W₂, thus reducing resources needed to send a CSIreport.

Upon receiving the variation indicators through the differential CSIreport B, the base station 702 can derive ΔV(t₂) based on the variationindicators. Using the prediction model where K is 2 (i.e., V(2)=a₁V(1)),the base station 702 can calculate V(t₂) based on V(t₁) obtainedpreviously. Accordingly, the base station 702 can calculateV(t₂)=V(t₂)+ΔV(t₂). Further, based on V(t₂), the base station 702 canderive the values of W₂(t₂).

Subsequently, at t₃, the UE 704 performs another set of CSI measurementsand determines the values of W₂(t₃). Accordingly, the UE 704 cangenerate V(t₃). Further, using the prediction model where K is 2 (i.e.,V(3)=a₂V(2)+a₁V(1)), the UE 704 can calculate V(t₃) based on V(t₁) andV(t₂). The UE 704 can calculate a difference between V(t₃) and V(t₃):

ΔV(t ₃)=V(t ₃)− V (t ₃).

The UE 704 can determine elements of ΔV(t₃) that are not zero andgenerate variation indicators indicating those non-zero elements ofΔV(t₃). Subsequently, at t₃′, the UE 704 sends to the base station 702 adifferential CSI report C containing the variation indicators.

Upon receiving the variation indicators through the differential CSIreport C, the base station 702 can derive ΔV(t₃) based on the variationindicators. Using the prediction model where K is 2 (i.e.,V(3)=a₂V(2)+a₁V(1)), the base station 702 can calculate V(t₃) based onV(t₂) and V(t₁) obtained previously. Accordingly, the base station 702can calculate V(t₃)=V(t₃)+ΔV(t₃). Further, based on V(t₃), the basestation 702 can derive the values of W₂(t₃).

In a second technique, the UE 704 and the base station 702 do not usethe prediction model of the first technique. As described supra, at t₁,the UE 704 performs a set of CSI measurements and determines W₂(t₁). Att₁′, the UE 704 sends a full CSI report A, which includes indicators(e.g., PMIs) indicating W₂(t₁). The base station 702 receives theindicators and accordingly can derive W₂(t₁).

In a first configuration of the second technique, the UE 704 may beconfigured to use the Type-II Codebook or Enhanced Type-II Codebook todetermine W₂ ^(Type-II)(t₁). Subsequently, at t₂, the UE 704 performsanother set of CSI measurements and determines W₂ ^(Type-II)(t₂)according to the Type-II Codebook. The UE 704 can calculate a differencebetween W₂ ^(Type-II)(t₂) and W₂ ^(Type-II)(t₁):

ΔW ₂(t ₂)=W ₂ ^(Type-II)(t ₂)−W ₂ ^(Type-II)(t ₁)

The UE 704 can determine elements of ΔW₂(t₂) that are not zero andgenerate variation indicators indicating those non-zero elements ofΔW₂(t₂). Subsequently, at t₂′, the UE 704 sends to the base station 702a differential CSI report B containing the variation indicators.

Upon receiving the variation indicators through the differential CSIreport B, the base station 702 can derive ΔW₂(t₂) based on the variationindicators. The base station 702 also obtained W₂ ^(Type-II)(t₁) basedon the full CSI report A. Accordingly, the base station 702 cancalculate W₂ ^(Type-II)(t₂)=W₂ ^(Type-II)(t₁)+ΔW₂(t₂).

In a second configuration of the second technique, the UE 704 may beconfigured to use the Type-I Codebook to determine W₂ ^(Type-I)(t₁).Subsequently, at t₂, the UE 704 performs another set of CSI measurementsand determines W₂ ^(Type-II)(t₂) according to the Type-II Codebook. TheUE 704 can determine a difference between W₂ ^(Type-II)(t₂) and W₂^(Type-I)(t₁):

ΔW ₂(t ₂)=W ₂ ^(Type-II)(t ₂)−W ₂ ^(Type-I)(t ₁)

ΔW₂(t2) includes elements that are in both W₂ ^(Type-II)(t₂) and W₂^(Type-I)(t₁) as well as elements that are in W₂ ^(Type-II) (t₂) but arenot in W₂ ^(Type-I)(t₁). The UE 704 can determine elements of ΔW₂(t₂)that are not zero and generate variation indicators indicating thosenon-zero elements of ΔW₂(t₂). Subsequently, at t₂′, the UE 704 sends tothe base station 702 a differential CSI report B containing thevariation indicators.

Upon receiving the variation indicators through the differential CSIreport B, the base station 802 can derive ΔW₂(t₂) based on the variationindicators. The base station 702 also obtained W₂ ^(Type-I)(t₁) based onthe full CSI report A. Accordingly, the base station 702 can calculateW₂ ^(Type-II)(t₂)=W₂ ^(Type-I)(t₁)+ΔW₂(t₂).

FIG. 9 is a diagram 900 illustrating the second technique describedsupra for CSI reporting. In this example of the second configuration ofthe second technique, the UE 704 is configured to use the EnhancedType-II Codebook to determine W₂ ^(eType-II), which is associated with atwo-dimensional space 910 has a delay dimension at X-axis and a spacedimension at Y-axis. The X-axis has delay indices τ₀, τ₁, τ₂, τ_(3,) . .. that indicate different delay periods. The Y-axis has space indicesα₀, α₁, α₂, α₃, . . . that indicate different space locations.

Using the example described supra referring to FIG. 8, the UE 704performs a set of CSI measurements at t₁. Based on the measurements, theUE 704 determines that signals (or pulses) received from a beam atlocation α₃ with a delay period τ₀ are optimal. Accordingly, the UE 704uses the Enhanced Type-II Codebook to determine W₂ ^(eType-II)(t₁),which corresponds to α₃ and τ₀ in the two-dimensional space 910. The UE704, at t₁′, sends a full CSI report A, which includes indicators (e.g.,PMIs) indicating W₂ ^(eType-II)(t₁). The base station 702 receives theindicators and accordingly can derive W₂ ^(eType-II)(t₁).

Subsequently, at t₂, the UE 704 performs another set of CSImeasurements. Based on the measurements, the UE 704 determines thatsignals (or pulses) received from a beam at location α₁ with a delayperiod τ₁ are optimal. Accordingly, the UE 704 determines W₂^(eType-II)(t₂) based on the measurements. Further, the UE 704 cancalculate a difference between W₂ ^(eType-II)(t₂) and W₂^(eType-II)(t₁):

ΔW ₂(t ₂)=W ₂ ^(eType-II)(t ₂)−W ₂ ^(eType-II)(t ₁)

The ΔW₂(t₂) specifies that the space index of the optimal signals/pulsesmoved down along the Y-axis for [α₃−α₁] and the delay index the optimalsignals/pulses moved right along the X-axis for [τ₁−τ₀]. The ΔW₂(t₂) mayalso specify amplitude/phase change from t₁ to t_(2.) Accordingly, att₂′, the UE 704 may send a differential CSI report B containingvariation indicators indicating the changes of space indices and delayindices. Upon receiving the variation indicators through thedifferential CSI report B, the base station 702 can derive ΔW₂(t₂) basedon the variation indicators. The base station 702 also obtained W₂^(eType-II)(t₁) based on the full CSI report A. Accordingly, the basestation 702 can calculate W₂ ^(eType-II)(t₂)=W₂ ^(eType-II)(t₁)+ΔW₂(t₂).

Subsequently, at t₃, the UE 704 performs another set of CSImeasurements. Based on the measurements, the UE 704 determines thatsignals (or pulses) received from beams at locations α₁ and α₂ with adelay period τ₁ are optimal. Accordingly, the UE 704 determines W₂^(eType-II)(t₃) Further the UE 704 can calculate a difference between W₂^(eType-II)(t₃) and W₂ ^(eType-II)(t₂):

ΔW ₂(t ₃)=W ₂ ^(eType-II)(t ₃)−W ₂ ^(eType-II)(t ₂)

The ΔW₂(t₃) specifies that the space index the optimal signals/pulsesmoves up along the Y-axis for [α₂−α₁] in one path and remains the samein another path. The ΔW₂(t₃) also specifies that the delay index theoptimal signals/pulses remains the same in both of the paths.Accordingly, at t₂′, the UE 704 may send a differential CSI report Ccontaining variation indicators indicating the changes of space indicesand delay indices. Upon receiving the variation indicators through thedifferential CSI report C, the base station 702 can derive ΔW₂(t₃) basedon the variation indicators. The base station 702 also obtained W₂^(eType-II)(t₂) based on the differential CSI report B. Accordingly, thebase station 702 can calculate W₂ ^(eType-II)(t₃)=W₂^(eType-II)(t₂)+ΔW₂(t₃).

In addition, other features can be employed to indicate to the basestation 702 and/or the UE 704 whether differential CSI reporting can beused. Referring back to FIG. 8, in a first feature, after successfullyreceiving the full CSI report A at t₁, the base station 702 can sendaperiodic CSI (A-CSI) trigger at a time point t₁₁. The A-CSI trigger att₁₁ indicates to the UE 704 that the base station 702 has successfullyreceived the full CSI report A and that the UE 704 can subsequently sendthe differential CSI report B. Accordingly, the UE 704 sends thedifferential CSI report B at t₂′ as described supra. When, after sendingthe full CSI report A, the UE 704 does not receive the A-CSI trigger att₁₁ or within a predetermined time duration, the UE 704 may determinethat the base station 702 has not successfully received the full CSIreport A. Accordingly, the UE 704 determines to send another full CSIreport containing PMIs (instead of the differential CSI report B) to thebase station 702 at t₂′.

In a second feature, after receiving each CSI report, the base station702 can send an ACK or NACK to the UE 704 to acknowledge whether thebase station 702 has successfully received the CSI report. The ACK/NACKcan be carried in a PDCCH, PDSCH, or MAC CE. In this example, afterreceiving the full CSI report A at t₁′, the base station 702 determinesthat the base station 702 has successfully received the full CSI reportA. Subsequently, at t₁₁, the base station 702 sends an ACK to the UE704. After knowing that the base station 702 has successfully receivedthe full CSI report A, the UE 704 can send the differential CSI report Bat t₂′ as described supra.

In a third feature, the UE 704 includes in each CSI report an indicatorindicating whether that CSI report is a full CSI report or adifferential CSI report. Further, when the CSI report is a differentialCSI report, the UE 704 can also include in that differential CSI reportan identifier identifying the prior reports based on which the variationindicators were calculated. For example, in the example of FIG. 8, theUE 704 can include in the differential CSI report C an identifieridentifying the differential CSI report B and the full CSI report A,bases on which the variation indicators contained in the differentialCSI report C were calculated.

FIG. 10 is a flow chart 1000 of a method (process) for performing CSIreporting. The method may be performed by a UE (e.g., the UE 704, theapparatus 1102, and the apparatus 1102′). In one configuration, atoperation 1002, the UE may inform a prediction model to network. Theprediction model may generate a set of reference values by performinglinear combination on one or more sets of prior values corresponding toa set of CSI parameters. In particular, a set of reference values aregenerated by the prediction model for a first time point based on theone or more sets of prior values for one or more time points prior tothe first time point. The set of CSI parameters contains CSI componentscorresponding a predefined codebook type

At operation 1004, the UE measure, at a second time point prior to thefirst time point, a second set of reference signals to determine asecond set of values corresponding to a set of CSI parameters. The oneor more sets of prior values include the second set of values. Atoperation 1006, the UE generate, based on the prediction model, a thirdset of values for third second time point prior to the first time point.One set of the prior values is derived from the third set of values.Subsequently, the UE enters operation 1020.

In another configuration, at operation 1012, the UE measures, at asecond time point prior to the first time point, a second set ofreference signals to determine, based on a codebook, a second set ofvalues corresponding to the set of CSI parameters. The second set ofvalues are used as a set of reference values. At operation 1014, the UEsends a second CSI report including indicators indicating the second setof values. Subsequently, the UE enters operation 1020.

At operation 1020, the UE measures, at the first time point, a first setof reference signals to determine a first set of values corresponding tothe set of CSI parameters. At operation 1022, the UE determines valuedifferences between the first set of values and the set of referencevalues corresponding to the set of CSI parameters. At operation 1024,the UE sends a first CSI report including variation indicatorsindicating the value differences.

In certain configurations, the UE receives, through a control channel,an indication indicating that the value differences are expected to besent, wherein the first CSI report are sent in response to receivingthat indication. In certain configurations, the UE receives anacknowledgement that the first CSI report has been correctly received ata base station. In certain configurations, the UE sends an indicationindicating that the value differences are included in the first CSIreport. In certain configurations, the UE sends an indication indicatingan identity of a reference CSI report that has been sent.

FIG. 11 is a diagram 1100 illustrating an example of a hardwareimplementation for an apparatus 1102′ employing a processing system1114. The apparatus 1102′ may be a UE. The processing system 1114 may beimplemented with a bus architecture, represented generally by a bus1124. The bus 1124 may include any number of interconnecting buses andbridges depending on the specific application of the processing system1114 and the overall design constraints. The bus 1124 links togethervarious circuits including one or more processors and/or hardwarecomponents, represented by one or more processors 1104, a receptioncomponent 1164, a transmission component 1170, a CSI measurementcomponent 1176, an variation calculation component 1178, a CSI Reportingcomponent 1182, and a computer-readable medium/memory 1106. The bus 1124may also link various other circuits such as timing sources,peripherals, voltage regulators, and power management circuits, etc.

The processing system 1114 may be coupled to a transceiver 1110, whichmay be one or more of the transceivers 354. The transceiver 1110 iscoupled to one or more antennas 1120, which may be the communicationantennas 352.

The transceiver 1110 provides a means for communicating with variousother apparatus over a transmission medium. The transceiver 1110receives a signal from the one or more antennas 1120, extractsinformation from the received signal, and provides the extractedinformation to the processing system 1114 specifically the receptioncomponent 1164 In addition, the transceiver 1110 receives informationfrom the processing system 1114 specifically the transmission component1170, and based on the received information, generates a signal to beapplied to the one or more antennas 1120.

The processing system 1114 includes one or more processors 1104 coupledto a computer-readable medium/memory 1106. The one or more processors1104 are responsible for general processing, including the execution ofsoftware stored on the computer-readable medium/memory 1106. Thesoftware, when executed by the one or more processors 1104, causes theprocessing system 1114 to perform the various functions described suprafor any particular apparatus. The computer-readable medium/memory 1106may also be used for storing data that is manipulated by the one or moreprocessors 1104 when executing software. The processing system 1114further includes at least one of the reception component 1164, thetransmission component 1170, the CSI measurement component 1176, thevariation calculation component 1178, and the CSI Reporting component1182. The components may be software components running in the one ormore processors 1104, resident/stored in the computer readablemedium/memory 1106, one or more hardware components coupled to the oneor more processors 1104, or some combination thereof. The processingsystem 1114 may be a component of the UE 350 and may include the memory360 and/or at least one of the TX processor 368, the RX processor 356,and the communication processor 359.

In one configuration, the apparatus 1102/apparatus 1102′ for wirelesscommunication includes means for performing each of the operations ofFIG. 10. The aforementioned means may be one or more of theaforementioned components of the apparatus 1102 and/or the processingsystem 1114 of the apparatus 1102′ configured to perform the functionsrecited by the aforementioned means.

As described supra, the processing system 1114 may include the TXProcessor 368, the RX Processor 356, and the communication processor359. As such, in one configuration, the aforementioned means may be theTX Processor 368, the RX Processor 356, and the communication processor359 configured to perform the functions recited by the aforementionedmeans.

It is understood that the specific order or hierarchy of blocks in theprocesses/flowcharts disclosed is an illustration of exemplaryapproaches. Based upon design preferences, it is understood that thespecific order or hierarchy of blocks in the processes/flowcharts may berearranged. Further, some blocks may be combined or omitted. Theaccompanying method claims present elements of the various blocks in asample order, and are not meant to be limited to the specific order orhierarchy presented.

The previous description is provided to enable any person skilled in theart to practice the various aspects described herein. Variousmodifications to these aspects will be readily apparent to those skilledin the art, and the generic principles defined herein may be applied toother aspects. Thus, the claims are not intended to be limited to theaspects shown herein, but is to be accorded the full scope consistentwith the language claims, wherein reference to an element in thesingular is not intended to mean “one and only one” unless specificallyso stated, but rather “one or more.” The word “exemplary” is used hereinto mean “serving as an example, instance, or illustration.” Any aspectdescribed herein as “exemplary” is not necessarily to be construed aspreferred or advantageous over other aspects. Unless specifically statedotherwise, the term “some” refers to one or more. Combinations such as“at least one of A, B, or C,” “one or more of A, B, or C,” “at least oneof A, B, and C,” “one or more of A, B, and C,” and “A, B, C, or anycombination thereof” include any combination of A, B, and/or C, and mayinclude multiples of A, multiples of B, or multiples of C. Specifically,combinations such as “at least one of A, B, or C,” “one or more of A, B,or C,” “at least one of A, B, and C,” “one or more of A, B, and C,” and“A, B, C, or any combination thereof” may be A only, B only, C only, Aand B, A and C, B and C, or A and B and C, where any such combinationsmay contain one or more member or members of A, B, or C. All structuraland functional equivalents to the elements of the various aspectsdescribed throughout this disclosure that are known or later come to beknown to those of ordinary skill in the art are expressly incorporatedherein by reference and are intended to be encompassed by the claims.Moreover, nothing disclosed herein is intended to be dedicated to thepublic regardless of whether such disclosure is explicitly recited inthe claims. The words “module,” “mechanism,” “element,” “device,” andthe like may not be a substitute for the word “means.” As such, no claimelement is to be construed as a means plus function unless the elementis expressly recited using the phrase “means for.”

What is claimed is:
 1. A method of wireless communication of a userequipment (UE), comprising: measuring, at a first time point, a firstset of reference signals to determine a first set of valuescorresponding to a set of channel state information (CSI) parameters;determining value differences between the first set of values and a setof reference values corresponding to the set of CSI parameters; andsending a first CSI report including variation indicators indicating thevalue differences.
 2. The method of claim 1, wherein the set of CSIparameters contains CSI components corresponding a predefined codebooktype.
 3. The method of claim 1, wherein the set of reference values aregenerated by a prediction model for the first time point based on one ormore sets of prior values, corresponding to the set of CSI parameters,for one or more time points prior to the first time point.
 4. The methodof claim 3, wherein the prediction model generates the set of referencevalues by performing linear combination on the one or more sets of priorvalues.
 5. The method of claim 3, further comprising: informing theprediction model to network.
 6. The method of claim 3, furthercomprising: measuring, at a second time point prior to the first timepoint, a second set of reference signals to determine a second set ofvalues corresponding to the set of CSI parameters, wherein the one ormore sets of prior values include the second set of values.
 7. Themethod of claim 3, further comprising: generating, based on theprediction model, a second set of values for a second time point priorto the first time point, wherein one set of the prior values is derivedfrom the second set of values.
 8. The method of claim 1, furthercomprising: measuring, at a second time point prior to the first timepoint, a second set of reference signals to determine, based on acodebook, a second set of values corresponding to the set of CSIparameters, wherein the set of reference values are the second set ofvalues.
 9. The method of claim 8, further comprising: sending a secondCSI report including indicators indicating the second set of values. 10.The method of claim 1, further comprising: receiving, through a controlchannel, an indication indicating that the value differences areexpected to be sent, wherein the first CSI report are sent in responseto receiving that indication.
 11. The method of claim 1, furthercomprising: receiving an acknowledgement that the first CSI report hasbeen correctly received at a base station.
 12. The method of claim 1,further comprising: sending an indication indicating that the valuedifferences are included in the first CSI report.
 13. The method ofclaim 1, further comprising: sending an indication indicating anidentity of a reference CSI report that has been sent.
 14. An apparatusfor wireless communication, the apparatus being a user equipment (UE),comprising: a memory; and at least one processor coupled to the memoryand configured to: measure, at a first time point, a first set ofreference signals to determine a first set of values corresponding to aset of channel state information (CSI) parameters; determine valuedifferences between the first set of values and a set of referencevalues corresponding to the set of CSI parameters; and send a first CSIreport including variation indicators indicating the value differences.15. The apparatus of claim 14, wherein the set of CSI parameterscontains CSI components corresponding a predefined codebook type. 16.The apparatus of claim 14, wherein the set of reference values aregenerated by a prediction model for the first time point based on one ormore sets of prior values, corresponding to the set of CSI parameters,for one or more time points prior to the first time point.
 17. Theapparatus of claim 16, wherein the prediction model generates the set ofreference values by performing linear combination on the one or moresets of prior values.
 18. The apparatus of claim 16, wherein the atleast one processor is further configured to: inform the predictionmodel to network.
 19. The apparatus of claim 16, wherein the at leastone processor is further configured to: measure, at a second time pointprior to the first time point, a second set of reference signals todetermine a second set of values corresponding to the set of CSIparameters, wherein the one or more sets of prior values include thesecond set of values.
 20. A computer-readable medium storing computerexecutable code for wireless communication of a user equipment (UE),comprising code to: measure, at a first time point, a first set ofreference signals to determine a first set of values corresponding to aset of channel state information (CSI) parameters; determine valuedifferences between the first set of values and a set of referencevalues corresponding to the set of CSI parameters; and send a first CSIreport including variation indicators indicating the value differences.